1. Field of the Invention
The present invention concerns a high resolution, one-way clutch, usable, for example, in an automatic slack adjuster for a vehicle brake, having a graduated saw-tooth engagement and a compact construction.
2. Description of Related Art
A saw-toothed one-way clutch (OWC) is particularly useful with automatic slack adjusters of several types that are appropriate for use in brake devices. In an arrangement of this type, during one part of a braking cycle, i.e. during brake apply or brake return, an input side of the OWC slips past the output side by an angle proportional to an increase in stroke due to brake wear. During the other part of the braking cycle, by contrast, the input side of the OWC engages with teeth of the output side and drives the output side. The output side of the OWC is designed to turn a worm-shaft, which turns a worm gear coupled to a brake cam shaft, thereby compensating for brake lining wear.
Some automatic slack adjusters use wrap spring clutches that employ close wound helical springs made from wire having a square or rectangular cross-section. These clutches are practically stepless, in that, following inputs in slipping directions, they will engage almost instantly in driving directions, and thus deliver outputs in response to very small inputs. A saw-tooth OWC, by contrast, will deliver an output only when an input is large enough to move an input side to engage with a next tooth in a series of teeth. In a saw-tooth OWC, therefore, the tooth spacing angle determines the resolution of the OWC. In practice, due to packaging constraints, the number of saw-teeth is limited to 72, which gives a resolution of five degrees. A slack adjuster stroke or resolution of five degrees, however, is considered too high, as it leaves little or no margin of error for regulatory compliance.
U.S. Pat. No. 8,302,742 to Louis et al., U.S. Pat. No. 8,302,744 to Louis, U.S. Pat. No. 8,453,805 to Louis, and U.S. Pat. No. 8,672,101 to Louis et al. disclose automatic slack adjusters with one-way clutches having varied configurations.
U.S. Pat. No. 8,602,188 to Louis discloses a high resolution clutch using graduated saw-tooth engagement. The clutch forming the subject matter of the Louis ('188) patent has driving and driven parts that are arranged in an axial stack and that engage or disengage by axial movement of floating teeth. Automatic slack adjusters typically have packaging constraints that make it difficult to utilize this arrangement, however, and so an alternative arrangement is desirable.
The entire disclosure of each of the U.S. Patents identified above is incorporated herein by reference as non-essential subject matter.